Observation of the shift of frequency chirp in two section distributed feedback semiconductor lasers

We report here on the control of frequency chirp of a two section InGaAsP-InP DFB laser by nonuniform current injection and the achievement of blue-shift optical signals from the two section DFB laser under direct current modulation. Through a measurement of the time-averaged power spectrum of the laser at 5-GHz modulation with fixed optical modulation index, the changing frequency chirp is demonstrated for various distributions of longitudinal photon density.